A desirable characteristic of x-ray sources, especially portable x-ray sources, is small size. An x-ray source can be comprised of an x-ray tube and a power supply. An x-ray source can have a high voltage sensing resistor used in the power supply circuit for sensing the tube voltage. The high voltage sensing resistor, due to a very high voltage across the x-ray tube, such as around 10 to 200 kilovolts, can require a very high resistance, such as around 10 mega ohms to 100 giga ohms for example. The high voltage sensing resistor can be a surface mount resistor and can be relatively large compared to other resistors. For example, resistor dimension can be around 12 mm×50 mm×1 mm in some power supplies. Especially in miniature and portable x-ray tubes, the size of this resistor can be an undesirable limiting factor in reduction of size of a power supply for these x-ray tubes.